clk: Add K210 pll support

This pll code is primarily based on the code from the kendryte standalone
sdk in lib/drivers/sysctl.c. k210_pll_calc_config is roughly analogous to
the algorithm used to set the pll frequency, but it has been completely
rewritten to be fixed-point based.

Signed-off-by: Sean Anderson <seanga2@gmail.com>
CC: Lukasz Majewski <lukma@denx.de>

2 files changed, 97 insertions, 0 deletions

diff --git a/test/dm/Makefile b/test/dm/Makefile
index 6c18fd04ce..5094a7866a 100644
--- a/test/dm/Makefile
+++ b/test/dm/Makefile
@@ -73,4 +73,5 @@ obj-$(CONFIG_DMA) += dma.o
 obj-$(CONFIG_DM_MDIO) += mdio.o
 obj-$(CONFIG_DM_MDIO_MUX) += mdio_mux.o
 obj-$(CONFIG_DM_RNG) += rng.o
+obj-$(CONFIG_CLK_K210_SET_RATE) += k210_pll.o
 endif
diff --git a/test/dm/k210_pll.c b/test/dm/k210_pll.c
new file mode 100644
index 0000000000..54764f269c
--- /dev/null
+++ b/test/dm/k210_pll.c
@@ -0,0 +1,96 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2020 Sean Anderson <seanga2@gmail.com>
+ */
+
+#include <common.h>
+/* For DIV_ROUND_DOWN_ULL, defined in linux/kernel.h */
+#include <div64.h>
+#include <dm/test.h>
+#include <kendryte/pll.h>
+#include <test/ut.h>
+
+static int dm_test_k210_pll_calc_config(u32 rate, u32 rate_in,
+					struct k210_pll_config *best)
+{
+	u64 f, r, od, max_r, inv_ratio;
+	s64 error, best_error;
+
+	best_error = S64_MAX;
+	error = best_error;
+	max_r = min(16ULL, DIV_ROUND_DOWN_ULL(rate_in, 13300000));
+	inv_ratio = DIV_ROUND_CLOSEST_ULL((u64)rate_in << 32, rate);
+
+	/* Brute force it */
+	for (r = 1; r <= max_r; r++) {
+		for (f = 1; f <= 64; f++) {
+			for (od = 1; od <= 16; od++) {
+				u64 vco = DIV_ROUND_CLOSEST_ULL(rate_in * f, r);
+
+				if (vco > 1750000000 || vco < 340000000)
+					continue;
+
+				error = DIV_ROUND_CLOSEST_ULL(f * inv_ratio,
+							      r * od);
+				/* The lower 16 bits are spurious */
+				error = abs((error - BIT(32))) >> 16;
+				if (error < best_error) {
+					best->r = r;
+					best->f = f;
+					best->od = od;
+					best_error = error;
+				}
+			}
+		}
+	}
+
+	if (best_error == S64_MAX)
+		return -EINVAL;
+	return 0;
+}
+
+static int dm_test_k210_pll_compare(struct k210_pll_config *ours,
+				    struct k210_pll_config *theirs)
+{
+	return (u32)ours->f * theirs->r * theirs->od !=
+	       (u32)theirs->f * ours->r * ours->od;
+}
+
+static int dm_test_k210_pll(struct unit_test_state *uts)
+{
+	struct k210_pll_config ours, theirs;
+
+	/* General range checks */
+	ut_asserteq(-EINVAL, k210_pll_calc_config(0, 26000000, &theirs));
+	ut_asserteq(-EINVAL, k210_pll_calc_config(390000000, 0, &theirs));
+	ut_asserteq(-EINVAL, k210_pll_calc_config(2000000000, 26000000,
+						  &theirs));
+	ut_asserteq(-EINVAL, k210_pll_calc_config(390000000, 2000000000,
+						  &theirs));
+	ut_asserteq(-EINVAL, k210_pll_calc_config(1500000000, 20000000,
+						  &theirs));
+
+	/* Verify we get the same output with brute-force */
+	ut_assertok(dm_test_k210_pll_calc_config(390000000, 26000000, &ours));
+	ut_assertok(k210_pll_calc_config(390000000, 26000000, &theirs));
+	ut_assertok(dm_test_k210_pll_compare(&ours, &theirs));
+
+	ut_assertok(dm_test_k210_pll_calc_config(26000000, 390000000, &ours));
+	ut_assertok(k210_pll_calc_config(26000000, 390000000, &theirs));
+	ut_assertok(dm_test_k210_pll_compare(&ours, &theirs));
+
+	ut_assertok(dm_test_k210_pll_calc_config(400000000, 26000000, &ours));
+	ut_assertok(k210_pll_calc_config(400000000, 26000000, &theirs));
+	ut_assertok(dm_test_k210_pll_compare(&ours, &theirs));
+
+	ut_assertok(dm_test_k210_pll_calc_config(27000000, 26000000, &ours));
+	ut_assertok(k210_pll_calc_config(27000000, 26000000, &theirs));
+	ut_assertok(dm_test_k210_pll_compare(&ours, &theirs));
+
+	ut_assertok(dm_test_k210_pll_calc_config(26000000, 27000000, &ours));
+	ut_assertok(k210_pll_calc_config(26000000, 27000000, &theirs));
+	ut_assertok(dm_test_k210_pll_compare(&ours, &theirs));
+
+	return 0;
+}
+DM_TEST(dm_test_k210_pll, 0);